1. Technical Field
The present invention relates to computer systems having optical communication interface ports and, more particularly, to personal computer systems with serial infrared ports which can communicate with other serial IR port-equipped devices.
2. Related Art
Recently, there has been a tremendous increase in the number of infrared-equipped devices, such as desktop computers, portable computers, personal digital assistants (PDAs), digital cameras, personal communications services (PCS) handsets, and the like. Much of the credit for the dramatic rise in the use of infrared technology is due to the Infrared Data Association (IrDA), a non-profit international standards organization that was founded in 1993. The IrDA is responsible for developing and promoting hardware and software protocol standards to the infrared communications links in computing communications, and electronics consumer devices.
IrDA's infrared standards are now accepted by computer and telecommunications hardware and software manufacturers worldwide. The IrDA serial infrared (SIR) physical layer link specification Versions 1.0, 1.1 and 1.2 are provided to facilitate the point-to-point communication between infrared interface port-equipped electronic devices (e.g., computers and peripheral devices) using directed half duplex serial infrared communications links through free space. The documents specify the optical media interface, and 0.576 Mbps, 1.152 Mbps and 4.0 Mbps modulation and demodulation. They contain specifications for the Active Output Interface and the Active Input Interface, and for the overall link.
Many of recent computers and peripheral devices are equipped with an infrared communication feature that allows point-to-point communication, and almost all of them may include IrDA devices. Infrared is a form of invisible electromagnetic radiation that travels in wavelengths greater than those of visible light and shorter than those of microwaves. Just as television remote control which uses infrared waves to transmit user's control information to televisions, computers and peripheral devices use infrared waves to transmit user's control information. Examples of contemporary communication devices using infrared technology are disclosed in U.S. Pat. Nos. 5,099,346 and 5,247,380 for Infrared Communication Network issued to Lee et al., U.S. Pat. No. 5,416,627 for Method And Apparatus For Two Way Infrared Communications issued to Wilmoth, U.S. Pat. No. 5,564,020 for Apparatus For Reducing Interference Between A Computer Device And A Radio Transceiver Utilizing Separated Units With An Infrared Link issued to Rossi, U.S. Pat. No. 5,600,471 for Optical Wireless Data Transmission System And Optical Wireless Data Transmitting/Receiving Apparatus issued to Hirohashi et al., U.S. Pat. No. 5,636,264 for Radio Telephone System Which Utilizes An Infrared Signal Communication Link issued to Sulavuori, U.S. Pat. No. 5,668,977 for Dockable Computer System Capable Of Electric And Electromagnetic Communication issued to Swanstrom et al., and U.S. Pat. No. 5,682,379 for Wireless Personal Local Area Network issued to Mahany et al.
For computers and peripheral devices, infrared interface ports (i.e., infrared transceivers) are installed at respective devices, and infrared communications work best when an infrared interface port of the transmitting device is aligned within 15 degrees (up, down, left, or right) of an infrared interface port of the receiving device. As long as the transceiver is properly aligned within this 30 degrees cone, connectivity will occur at reasonable distances (e.g., about 3 meters). In practice, as I have observed however, it is extremely difficult to align the computers and peripheral devices within allowable link angle and distance. The problem is magnified for relatively heavy infrared-compatible desktop computers or printers with less mobility than portable computers since the infrared interface ports of the respective computers and peripheral devices are fixed to the housings, and the optical axes of the infrared interface ports are normal to the surface of the housings.